Suppression of the Primary and Secondary Immune Response of the Mouse by Phytohemagglutinin

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Abstract
Summary: The effect of phytohemagglutinin on the immune response of mice to sheep erythrocytes has been investigated by measuring the 19S and 7S antibody-producing capacity of isolated spleen cells. The administration of phytohemagglutinin (PHA) simultaneously with, or prior to, the injection of sheep red blood cells induced a marked depression of both the primary and secondary immune response. On the other hand, PHA given after the antigen led to no modification of the antibody response. The observed immune suppression was transient, and disappeared within 4 days after PHA administration; thereafter a normal response to antigenic challenge was observed. The magnitude of the immune suppression was dose-dependent and no effects were detected when heat-inactivated PHA was used.